Method and apparatus for separating co-mingled materials

ABSTRACT

A material separating apparatus which is particularly suitable for sorting different forms of waste material including a carrier, generally a table (1) having a surface (10) onto which material can be deposited; and a drive element (3) for providing the carrier surface with a reciprocating motion in the plane of the carrier surface; the drive element being arranged to provide, in use, an abrupt change of direction of the carrier surface at each end of its travel to provide a motion to cause different components of the material to be separated in consequence of obtaining different velocities in dependence on their physical properties, and the table surface having different sloping zones for channeling out different materials. The drive element uses an offset crank linkage which collapses at the end of travel in each direction enabling the inertia of the table to continue until it hits a stop and is then drawn back in the reverse direction by the linkage.

The present invention relates to an apparatus and a method forseparating material, in particular waste material. Such material isnormally in a co-mingled state and can consist of newspapers, cardboard,plastic bottles, glass, organic waste and other such items. The sortingof waste material is a major problem and many different systems havebeen developed in order to extract various components of the waste. Forexample, it is possible to extract metal components of the waste usingmagnetic or eddy current separators where appropriate. However, mostexisting systems can effectively sort only a limited number of types ofwaste and the present invention is directed at the provision of a systemwhich can improve on this.

We have found that objects may be separated if placed on a carriersurface and that carrier surface is provided with a movement in theplane of the carrier surface. This effect can be partially accounted forbecause different objects experience different frictional forces and,therefore, are accelerated and decelerated by differing amounts.

Further certain objects may momentarily leave the carrier surface atwhich point air resistance becomes a dominant factor. In certaincircumstances objects may bounce along the carrier surface and this cancause separation. The effect can be particularly pronounced if themovement of the carrier surface is such that resonance occurs so thatcertain objects only (or more frequently) contact the table when it ismoving in one particular direction. The physical properties of theobjects and the carrier surface will effect the natural frequency withwhich an object will bounce.

Both the velocity and acceleration with which the carrier surface movesare important in the separation process. Objects have a co-efficient oflimiting friction and co-efficient of dynamic friction. Theseco-efficients depend on the composition and nature of surface of theobject concerned. When the carrier surface is given a certainacceleration, the limiting friction will be overcome for some objectsbut not others. Those objects whose limiting friction is not overcome,will remain stationary relative to the carrier surface. If the limitingfriction is overcome for a particular object, that object will then movewith a certain velocity relative to the carrier surface. A frictionalforce, however, will still act on this object, and this force will bedependent on the object's co-efficient of dynamic friction. Thisfrictional force will tend to decrease the relative velocity between thecarrier surface and the object concerned. A moving object which is incontact with the carrier surface will always experience a force in thedirection in which the table is moving. Therefore, if the table spendslonger moving in one direction than another, each object will experiencea force for a greater period of time in one direction than the other.This can have the effect of providing different objects with differentvelocities and thereby yield separation.

When objects leave the carrier surface the distance that they travelwill depend on their momentum and the air resistance that theyexperience. The mass, density, surface area and the surfacecharacteristics of the objects are therefore important. Differentobjects will leave the carrier surface dependent on its velocity andacceleration. If the surface spends longer travelling one direction thananother, objects will tend to pick up more speed in that direction.

The separation effect can be enhanced by providing the carrier surfacewith variable acceleration so that, at different times, the limitingfriction for different objects is overcome.

The separation may be amplified by using a carrier surface having avariable slope. Objects which have obtained a large velocity in acertain direction will tend to proceed in that direction. Objects withlesser velocities, will spend longer on the slope and therefore gain ahigher velocity down the slope due to the action of gravity. The slopeof the carrier surface can also encourage certain components of thematerial to become airborne.

Other factors such as the jostling between adjacent objects moving atdifferent velocities, may also heighten the separation effect. Othersurface force effects such as static electrical attraction may also playa role in the separation effect.

According to the present invention there is provided a materialseparating apparatus comprising:

a carrier surface onto which material can be deposited; and

a drive means for providing said carrier surface with a motion in theplane of said carrier surface;

the arrangement being such that in use, said carrier surface acceleratesand/or decelerates the material and different components of the materialare separated in consequence of obtaining different velocities independence on their physical properties.

According to another aspect of the invention there is provided a methodof separating material comprising the steps of:

depositing material on a carrier surface;

providing said carrier surface with a motion in the plane of saidcarrier surface; and

retrieving separated material;

said carrier surface accelerating and/or decelerating the material anddifferent components of the material being separated in consequence ofobtaining different velocities in dependence on their physicalproperties.

A generally preferred manner of carrying out the invention is to providesaid carrier surface with a conveying motion. Then separation occurs dueto some articles being conveyed and some not being conveyed, or beingconveyed at a greater or lesser speed, due to the differential frictionand/or differing tendencies to leave the carrier surface.

In a specific aspect of the invention the carrier surface may comprise atable member which is caused to move with a generally oscillatorymotion, but having a stroke in a first direction slower than a stroke ina return direction.

The oscillatory motion may be made such that, the acceleration duringthe change from the first direction to the return direction is greaterthan the acceleration during the chance from the return direction to thefirst direction.

Alternatively, the conveyor surface may be part of a conveyor whereconveying movement only occurs in one direction and the speed ofmovement is selected to enable separation to occur in that direction. Anexample of such a form of conveyor is where a stationary grid carrierhas been meshed with a conveying grid which rises above the surface whenmoving in one direction, to provide conveying in that direction, andthen drops below the level of the stationary grid conveyor in the returnstroke.

A further possibility is to have a rotary table where a centrifugalforce is applied to objects dependent on the relative friction and theirtendency to leave the carrier surface.

Other combinations of linear and rotary motion can be provided to giveother forms of motion that provide separation of the objects.

It is advantageous to be able to adjust the speed, frequency andduration of the motion of the carrier surface.

Preferably the carrier surface of the table member consists of aplurality of sections. Provision of slope adjustment means, so that itis possible to adjust the slope of any one of these sections, yieldsfurther advantages.

Preferably there is at least one feed chute for delivering material tothe carrier surface. One or more of the feed chutes may be vibratedduring use. If there are two or more feed chutes, then gaps can beprovided between successive feed chutes so that some material isextracted before reaching the carrier surface.

As a result of these features, different types of waste can be sortedfrom one another by using a simple mechanical device.

A particular advantage is that the separating apparatus can remove alarge proportion of the glass contained in waste material and is notdamaged by glass. Once the majority of the glass has been extracted fromthe waste, the remaining material can be sorted using apparatus havingrubber components which although cost effective are easily damaged bybroken glass.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is a side elevation of the separating apparatus;

FIG. 2 is a plan view of the separating apparatus;

FIGS. 3a-3d are cross sections of the table member along lines A--A,B--B, C--C, D--D of FIG. 2;

FIG. 4 is a side elevation of the drive means;

FIGS. 5a and 5b are front and side elevations of the flywheelrespectively;

FIG. 6 is a front view of the flywheel showing loci of the pin; and

FIGS. 7a and 7b are a plan view and front elevation of the table armlinkage respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The material separating apparatus comprises three main parts, a tablemember 1, a chute arrangement 2, and a drive means 3.

The table member 1 has an upper carrier surface 10. The carrier surface10 is made up of six separate but integral sections. These sections areright and left outer sections 101a, 101b, right and left inner sections102a, 102b, and right and left front sections 103a, 103b.

The carrier surface 10 has a rear 105, a front 106, a right side 107 anda left side 108. The carrier surface 10 is symmetrical about a symmetryline 104. The carrier surface is divided by a transverse line 109. Theright and left inner sections 102a, 102b are disposed either side of thesymmetry line 104, towards the rear 105 of the table member 1. The rightand left outer sections 101a, 101b are disposed outwardly from the rightand left inner sections 102a, 102b. The transverse line 109 forms oneend of the inner and outer sections 101a, 101b, 102a, 102b. The rightand left front sections 103a, 103b are disposed forwards of thetransverse line 109.

All of the carrier surface sections slope downwards towards the front106 of the table member 1. The forwards slope of the front sections103a, 103b is steeper than the forwards slope of the inner and outersections of 101a, 101b, 102a, 102b.

All of the right side sections 101a, 102a, 103a, slope towards the rightside 107 of the table member 1. All of the left side sections 101b,102b, 103b, slope towards the left side 108 of the table member 1.

Referring to FIG. 3, the sideways slope of the inner sections 102a, 102bis greater on line A--A, than on the line B--B. The sideways slope ofthe outer sections 101a, 101b is greater at the line B--B, than at theline A--A. The sideways slope of the front sections 103a, 103b, isgreater at the line C--C, than at the line D--D. The sideways slope ofthe outer sections 101a, 101b is always greater than the sideways slopeof the inner sections 102a, 102b.

Means are provided to alter the slope of the various sections of thetable member.

The apparatus includes a stop means comprising right and left stops110a, 110b and right and left stop plates 111a, 111b. Referring to FIGS.1 and 2, the right and left stops 110a, 110b are attached to the rightand left sides 107, 108 of the table member 1. The right and left stopplates 111a, 111b are securely mounted to a stationary frame (not shown)and are disposed on either side of the table member 1 so that they caninteract with the right and left stops 110a, 110b, respectively.

The chute arrangement 2 comprises a first chute 21 and a second chute22, and a pre-sort collection member 23. The first and second chutes 21,22, are separated by a gap G and a forward end of the first chute 21 isspaced upwardly from a rear end of the second chute 22 by a heightspacing H. The pre-sort collection member 23 is disposed under the gap Gand below the level of the first and second feed chutes 21, 22. Thechute arrangement is held in a frame (not shown) and is disposedupwardly and rearwardly of the table member 1. The forward slope of thefirst chute 21 is steeper than that of the second chute 22.

Referring to FIG. 4, the drive means 3 comprises three main components,a table arm linkage 30, a pivot arm linkage 31 and the flywheel 32.

The pivot arm linkage 31 is rotatably mounted about the first axis 311and comprises a slot 312.

Table arm linkage 30 comprises a first member 301 and a second member302. The first member 301 is rotatably connected to the second member302 by a connector 303. The first member 301 is further connected via aconnector 33, to the pivot arm linkage 31. The second member 302 isfurther connected via a connector 34 to the table member 1. The firstmember 301 comprises a first side wall 301a and a second side wall 301b.These side walls sandwich the upper end of the pivot arm linkage 31 andthe second member 302. The second member 302 may pivot round theconnector 303, but its range of motion is constrained between an upperlimit position 302u and a lower position limit 302d.

The flywheel 32 is arranged to be rotated around a second axis 321. Theflywheel has a pin 322 spaced from this second axis 321. The pin 322 islocated in the slot 312 of the pivot arm linkage 31. The pin 322 has anannular lip 323 which keeps the pin correctly located in the slot 312.

In operation, material is delivered to the first chute 21, from there itpasses onto the second chute 22 and onwards to the table member 1.However, some of the material will fall through the gap G into thepre-sort collection member 23. This material may then be removed forfurther separation. Certain components of the waste, particularlyplastic film, paper, organic material and fine powders, will tend tofall through the gap G.

Because the slope of the second chute 22 is shallower than the slope ofthe first chute 21, material will tend to be slowed down during its pathacross the second chute and, therefore, be delivered to the table with areduced velocity.

The chute arrangement plays some part in the separation of material andits separating characteristics may be changed by vibrating the chutes,or by altering the width of the gap G, the size of the height spacing H,or the slope of either or both of the chutes. The dotted arrows 24 and25 show various paths of the material through the chute arrangement.

In operation, the table member 1 is driven in an uneven oscillatorymotion, such that its speed during a forward stroke is less than itsspeed during a return stroke. Further, the table member 1 is made toexecute a snatch motion at the change of direction from the forward tothe return direction. That is to say, the acceleration during the changeof direction from the forward to return direction, is greater than theacceleration when the direction changes from the return to the forwarddirection. The material which is delivered to the table member 1 via thechute arrangement 2, will tend to be separated by these differingvelocities and accelerations. Items experiencing extremely high frictionwill not be conveyed. All other items will tend to be conveyed in theforward direction from the rear of the table 105 to the front of thetable 106. Those with the lowest friction will be generally expected toproceed in this direction most quickly. The various slopes of thedifferent sections of the table amplify this separating effect. Objectswhich have picked up a high forward velocity will tend to leave thetable member 1 towards the front, while those which have picked uplittle forward velocity will leave the table member 1 towards the sides.This is because the fast moving objects have less time in which toexperience the gravitational forces which act on them.

The amount of time objects spend airborne and the occurrence of anyresonance effects will also affect the paths followed by and the speedsof objects.

The arrangement of the drive means 3 is such that the table member 1will be moved faster in a return direction than in a forward direction,and that there will be a snatch action when the direction of motionchanges from the forward to the return direction. In operation, theflywheel 22 is rotated in an anti-clockwise sense. This causes the pin322 to run up and down the slot 312. The action of the pin 322 on theslot 312 makes the pivot arm linkage move in the forward and returndirections and consequently, the table arm linkage 30 moves in thesedirections, as does the table member 1.

Referring to FIG. 6, during the forward stroke the pin 322 moves from afirst pin position to 322a to a second pin position 322b, following alocus F. During the return stroke of the table, the pin moves from athird pin position 322c to a fourth pin position 322d, following a locusR. The locus F is longer than the locus R, and this longer locuscorresponds to a longer time because the flywheel rotates at a constantrate. As a result of this, the table member 1 spends a longer timemoving in the forward direction than it does in the return direction.This means that the table member 1 must move correspondingly faster inthe return direction. It will be appreciated that although the locus Fis longer than the locus R, the connector 33 moves the same distance inthe forward and return strokes because of the lever effect around thefirst axis 311.

The co-operation of the first and second members 301 and 302 and thestop means allow a snatch motion to be achieved as the direction of thetable is changed from the forward to the return direction. During afirst part of the forward stroke, the table arm linkage 30 is in acollapsed state; that is to say, the second member 302 has adoptedeither the upper limit position 302u or the lower limit position 302d.Towards the end of the forward stroke the speed of motion of the firstmember 301 is reduced because of the path of the pin 322, while thespeed of the table member 1 is almost constant because of its inertia.This tends to elongate the table arm linkage 30; that is to say, thesecond member 302 tends to adopt a central position. At this point theright and left stops 110a, 110b strike the right and left stop plates111a, 111b, which stops the table member 1 sharply and re-collapses thetable arm linkage 30. Now however, the first member 301 is starting tomove in the return direction and the table arm linkage 30 begins toelongate. When the table arm linkage 30 becomes fully elongated, thefirst member 301 is moving quickly in the return direction but the tablemember 1 is essentially stationary and therefore, the table member 1experiences a sudden force and is snatched quickly backwards.

The table arm linkage 30 remains in the elongated state until the pinreaches the fourth pin position 322d. At this point the inertia of thetable and the change of direction of the first member 301, tend tore-collapse the table arm linkage 30. Thus the table arm linkage 30adopts the collapsed state, ready for the start of the next forwardstroke.

To alter the length of the forward and return strokes the pivot armlinkage 31 may be made to pivot about any one of four pivot positions311a to 311d. The second and third pivot positions 311b, 311c aredisposed 19 mm either side of the first axis 311. The first and fourthpivot positions 311a, 311d, are disposed 19 mm outwardly of the secondand third pivot positions 311b, 311c, respectively.

The Apparatus can be driven at various speeds including 42, 51, 55, 64,69, 77 or 84 strokes per minute.

The flywheel 32 can be driven by an electric motor or any other suitablemeans.

In an alternative form of the invention other drive means can be usedwhich give the appropriate uneven reciprocal motion. For example springsmay be used which resist the motion in one direction but aid it in theother.

Alternatively a computer controlled drive means may be used.

In other alternatives the surface 10 of the table member 1 can compriseonly one or any other number of sections. One or more of these sectionsmay be substantially horizontal. One or more of these sections may besloped upwards towards the front and/or the sides of the table.

In further alternatives one or any other number of feed chutes could beused.

In an alternative method, material may be pre-sorted using an apparatusaccording to the present invention or any conventional means, before itis fed to the table member. Further, or alternatively, the material canbe further sorted once it has left the table member.

Amongst other things the apparatus and the method can be used toseparate material consisting of newspaper, cardboard, steel andaluminium cans, glass jars and bottles, plastic bottles, dairy producepots, plastic film and organic materials, wood and sawdust etc.

The separating characteristics of the apparatus may be altered bychanging a number of different factors. These include: the length ofstroke, the speed of stroke, frequency of stroke, the degree of tableslopes, the methods of feeding the table, the arrangement of the chutes,Experiments can be carried out in order to produce an apparatus givingthe separation effects desired.

An apparatus can be tuned to separate particular materials andadjustments can be made by an operator in response to the type of wastebeing delivered to the table. For example, if the waste contains a largeamount of glass the speed of oscillation can be increased to effectivelyproject the glass forward.

If a number of apparatuses according to the present invention are usedin series, each can be set up to most effectively separate a differentfraction of the waste.

Further the material of which the carrier surface is made and itsstructure will affect the behavior of the material which is deposited onthe carrier surface. The carrier surface can be metal such as steel oraluminium sheet or a plastics material. The carrier surface can bearranged so that its deformation is minimized or so that it supported insuch a way to encourage elastic deformation.

What is claimed is:
 1. A material separating apparatus comprising:Acarrier having a surface onto which material can be deposited; and adrive means for providing said carrier surface with a reciprocatingmotion in the plane of said carrier surface; the drive means beingprovided with stop means adapted, in use, to stop suddenly the motion ofthe carrier surface at one end of its travel, the abrupt change indirection of the carrier surface providing a motion which causesdifferent components of the material to be separated in consequence ofobtaining different velocities in dependence on their physicalproperties.
 2. A material separating apparatus according to claim 1 inwhich said motion is a reciprocating motion comprising a first stroke ina first direction and a second stroke in a return direction, and inwhich said second stroke is faster than said first stroke.
 3. A materialseparating apparatus according to claim 2 in which the acceleration ofthe carrier surface when its motion changes direction from the first tothe return direction is greater than the acceleration when the motion ofthe carrier surface changes from the return to the first direction.
 4. Amaterial separating apparatus according to claim 2 and furthercomprising an offset linkage for providing said first and second strokesof motion.
 5. A material separating apparatus according to claim 1 inwhich the carrier surface comprises a plurality of sections havingdifferent slopes, to channel components travelling at differentvelocities.
 6. A material separating apparatus according to claim 1 andfurther comprising an offset linkage for providing said first and secondstrokes of motion in which said offset linkage is arranged to ceaseproviding drive as it approaches an extreme of its stroke to enable saidstop means to operate in suddenly stopping the motion of the carriersurface, and, after the motion has stopped, to provide drive again in areverse direction.
 7. A material separating apparatus according to claim6 in which said offset linkage includes a pivotal link which enables thelinkage to collapse as it approaches extremes of its stroke so as todisengage drive for stopping and reversing motion of the carriersurface.
 8. A material separating apparatus according to claim 3 andfurther comprising an offset linkage for providing said first and secondstrokes of motion.
 9. A material separating apparatus according to claim2 in which the carrier surface comprises a plurality of sections havingdifferent slopes, to channel components travelling at differentvelocities.
 10. A material separating apparatus according to claim 3 inwhich the carrier surface comprises a plurality of sections havingdifferent slopes, to channel components travelling at differentvelocities.
 11. A material separating apparatus according to claim 4 inwhich the carrier surface comprises a plurality of sections havingdifferent slopes, to channel components travelling at differentvelocities.
 12. A material separating apparatus according to claim 8 inwhich the carrier surface comprises a plurality of sections havingdifferent slopes, to channel components travelling at differentvelocities.
 13. A method of separating material comprising the stepsof:depositing material on a carrier surface; providing said carriersurface with a reciprocating motion in the plane of said carriersurface; and retrieving separated material; said carrier surface beingarranged to stop suddenly at one end of its travel causing an abruptchange in direction so that different components of the material areseparated in consequence of obtaining different velocities in dependenceon their physical properties.